Such a method is known from EP-A-254,915, in which, in order to produce a light-transmitting, optical fiber, a hollow tube of thermoplastic material is filled with the monomer of the thermosetting polymer, which is then polymerized by subjecting the filled tube to a temperature treatment.
A drawback of this known process is the limited length in which the object can be obtained, while fibers, including optical fibers, are normally used in very great lengths. In addition, from lines 12-16 on page 4 and Example 1, lines 4-7 of page 19 of the aforementioned patent application it is apparent that the production rate is limited to between a few decimeters and a few meters per hour, which makes this process hardly applicable in economic terms.
Melt processing of thermosetting polymers, once they have cured is not possible. Therefore, manufacture of objects of thermosetting materials as a rule takes place by introducing the corresponding monomer into a mold of the desired shape and then polymerizing it, the resulting object having the shape of the mold. At low temperatures, for instance room temperature, most monomers of thermosetting polymers are liquids, which cannot be shaped to self supporting objects, so that spinning or extruding of the monomer does not yield continuous objects or running lengths which can be handled in further treatments. That is why for the continuous manufacture of continuous objects or running lengths of thermosetting polymers, in marked contrast to the situation for thermoplastic polymers, no economically applicable techniques are known. Patent publication JP-A-61/262707 does describe a controlled manner of gradual polymerization of a polymerizable monomer, yielding a prepolymer with a viscosity that makes it suitable for spinning, followed by spinning of the prepolymer--already possessing some internal cohesion due to the partial polymerization--and subsequent further polymerization. But this process requires very precise control and consequently has low flow through rates and it is economically unattractive because of the resulting low production speed.